An image forming device includes a device frame, a developing unit which is inserted into the device frame in a prescribed inserting direction, two terminals which are provided in the device frame, a metal conduction member which is provided in the developing unit and makes contact with at least one of the terminals, and a detecting unit which detects a presence or an absence of continuity between the terminals. Identification protrusions are fixed on an upper surface of the developing unit for determining compatibility between the developing unit and device frame.